Great Reed-warbler, Acrocephalus arundinaceus, is a species of passerine bird in the warbler family found in wetland and river and lake ecosystems. It is a widespread summer visitor to most of Europe. This species breeds mainly in beds of reed ( Phragmites ), locally in stands of reedmace ( Typha ), growing in fresh or brackish water and rarely, in willow bushes ( Salix ). It shows a preference for tall reeds with thick stems, especially next to open water (European Red List 2015).

Acrocephalus arundinaceus has a breeding population size of 1030000-1590000 pairs and a breeding range size of 1650000 square kilometres in the EU27. The breeding population trend in the EU27 is Stable in the short term and Unknown in the long term.

The EU population status of Acrocephalus arundinaceus was assessed as Secure, because the species does not meet any of the IUCN Red List criteria for threatened or Near Threatened, or the criteria for Depleted or Declining (the EU27 population or range has not declined by 20% or more since 1980).